Fluid trapping device



June 15, 1943. s. S(-.;HNELL 2,322,062

FLUID TRAPPING DEVICE Filed Feb. 19, 1942 2 Sheets-Sheet 1' INVENTOR i VE SCHNEL L ATTORNEY June 15, 1943. s. SCHNELL FLUID TRAPPiNG DEVICE Filed Feb. I 19, 1942 2 Sheets-Sheet 2 INVENTOR ST SCHNELL ATTORNEY Patented June 15, 19 43 PATENT OFFICE 2,322,062 I I ram rnarrmo onvrcn Steve Schnell, Kirkwood, Mo., asslgnor to Wagner Electric Corporation, St. Louis, Mo., a corporation oi Delaware Appiication February 19, 1942, Serial No. 431,488 I 14 Claims.

My invention relates to fluid pressure systems and more particularlyto means for trapping fluid under pressure in said system. i

One of the objects of my invention is to provide improved means for trapping fluid under pressure in a fluid pressure actuatingsystem and which can be operated to automatically release the trapped fluid pressure by are-application of fluid pressure from the source.

Another object of my invention is to associate with said fluid trapping means an expansible chamber which will be placed in communication with the portion of the fluid system in which fluid under pressure is to be trapped only when the trapping means is operated and then remain in saidcommunication only if the fluid pressure is above a predetermined value.

Still another object 01' my invention is to provide a trapping means for a fluid pressure system which can only be caused to be operative to maintain 'fluid trapped under pressure it the fluid placed under pressure is above a predetermined value. p

Yet another object of my invention is to provide improved means for actuating a trapping device for fluid under pressure which means will permit 1 operation of the device by a substantially uniform manual eflort. v v

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which Figure 1 isa schematic View of a fluid and treadle III which is connected to the bellcrank by a rod I l. The treadle is pivoted on the end of lever l2 employed to operate other mechanism on the airplane. It is seen from the construction described that lever i2 may be operated by movement of the heel portion of the treadle,

and the master cylinder operated by movement of the toe of the treadle.

My improved fluid pressure trapping device is indicated by thenumeral l3 and is interposed ,between conduits 2 and 3.

It isby means of this trapping device that fluid under pressure may be trapped in the brake operating fluid motor to hold the brakes applied under certain conditions, as will later become apparent.

As shown in Figure 2, the trapping device complates 2| and 22 andconnecting pins 23. The

end plate. 22 carries a rubber valve element 24 pressure system having associated therewith a fluid pressure trapping device embodying my invention; Figure 2 is a longitudinal sectional view of the trapping device, showing details thereoi; and Figure 3 is a sectional view taken on the line 3-8 of Figure 2.

Referring to the drawings, the braking system with which-I have associated my improved trapping device isshown as being one employed for operating the brakes oi! an airplane but it is to be'understood' that this is by way of example only since said trapping device may be employed in any fluid pressure system where it is found desirable. j As shown in Figure 1, the fluid pressure system comprises a pressure producing source in the form of a master cylinder device I, the outlet of which is connected by conduits 2 and 3 to brake 4. This brake embodies shoes 5 which-are actuated into engagement with drum 6 by a fluid motor Thepiston of the master cylinder (not shown) is adapted to be actuated to produce pressure by means of the piston rod 8, bellcrank 9,

for cooperation with a valve seat 25 surrounding the inner end of inlet passage I8. The other end plate 2| also carries a rubber valve elenient 26 for cooperation with a valve seat 2'! surrounding the inner end of passage I]. The end plates 2| and 22 are so spacedapart that only one of the valve elements carried thereby may be seated at a time to close the passages 'with which they are associated. A spring 28 acts on the cage to move it toward a position where the valve element 24 can engage seat 25 and also cause disengagement of the valve element 26 from seat 21.

The cylinder I6 has mounted therein a piston 29 normally biased by a strong coil spring 30 toward the end of the cylinder to which passage l'l connects. A perforated plug 3| closes the outer end of the cylinder and acts as an abutment for one end of thesprlng. The spring 30 is of such strength that'piston 29 must have acting thereon approximately three hundred pounds per square inch fluid pressure before the piston can be moved to compress the spring. The

build-upof the spring is such that when it is approximately half compressed, 'the piston must have acting thereon approximately four hundred and fifty pounds per square inch of fluid pressure, and to totally compress the spring there must be acting on the piston approximately six hundred pounds per square inch of fluid pressure.

In the casing I4 there is journaled a shaft 32, said shaft extending between the end plates 2| and 22 of the cage. This shaft is provided with a flat surface 33 on one side adjacent plate 2| and with a lobe 34 on the side adjacent plate 22. The shaft extends to the exterior of the casing and is sealed by a plug 35 and packing 36, there being a spring 31 for biasing shoulder 38 on the shaft against the packing. The outer end of the shaft has secured thereto an arm 39 for rotating the shaft. When the shaft is in the position shown in Figure 2, the flat surface 33 thereof will be turned at an angle from the vertical and the shaft will then hold the cage to the left so that valve element 26 will be in engagement with seat 21, and valve element 24 will be disengaged from seat 25. Thus passage l'l will be closed and passage l8 opened. If the shaft should be turned so that flat surface 331s in a vertical position, lobe 34 on the shaft will cause the cage to be positively moved to the right, as viewed in Figure 2, and thus cause valve element 26 to be disengaged from seat 21. As soon as valve element 26 is disengaged from the seat, spring 28 will be effective to move the cage so that valve element 24 will engage its seat 25 and close passage Ill.

The exterior of cylinder i6 has secured thereto a bracket 40 and pivoted on this bracket is a belicrank lever M having arms 42 and 43. The arms 52 has pivotally connected thereto one end of a link 44, the other end of the link being pivotally connected to the lower end of arm 39 by means of a pin 65 carried by said arm and passing through a slot 46 in the end of the link. The other arm 43 of the belicrank lever has connected thereto one end of a relatively strong coil spring 41, the other end of said spring being connected to the arm 39 intermediate its ends but closer to the end connected to shaft 32. The end of arm 42 of the belicrank lever has also connected thereto a flexible cable 48, the free end of' which is provided with a pull button 49. This flexible cable permits remote actuation of the belicrank lever and operation of the trapping device. The extent of movement of the belicrank lever by the cable is limited by a stop 50 carried on bracket Mi. This stop is also engaged by link 44 to limit clockwise movement of the belicrank lever and thus predetermine the anchored position of the left end of spring 41 when the cable is released.

In order that the fluid under pressure which enters cylinder i6 may be known, said cylinder is connected by a conduit to a pressure gauge 52. as indicated, the purpose of which will become apparent from the description of the operation of the trapping device. 7

Referring to the operation of the structure just described, the parts of the fluid trapping device will be in the full line positions shown when it is inoperative. Under these conditions spring 41 W11 act on arm 39 to so position the control shaft that the valve element 26 will be seated to close of! communication between chamber 15 and cylinder l6 through passage IT. The valve element 24 will be unseated. It is thus seen that there is free two-way communication between the master cylinder device and the fluid motor. Thus the brakes may be applied and released by operation of the master cylinder as a result of proper toe actuation of the treadie l0.

' on the cable 48 or holding it set.

When it is desired to trap fluid under pressure in the fluid motor I of the brake and thus hold the brake applied, the master cylinder is so operated as to place the fluid in the system under a pressure of four hundred and fifty pounds per square inch or more. The lever arrangement of the actuating mechanism for the trapping device and the relationship thereto of the spring 4'! and its strength is such that this fluid pressure of four hundred and flfty pounds per square inch or more must be obtained before the trapping device can be operative to hold fluid trapped without maintaining a continuous manual pull This value of four hundred and flfty pounds per square inch, of course, can be varied as, for example, by varying the strength of spring 41, changing the lengths of the arms of the belicrank lever, and so forth. To trap this fluid pressure, the master cylinder is held in an operative condition by the foot of the operator and cable 48 is pulled forwardly. This will result in the belicrank lever 4i being rotated in a counter-clockwise direction and to a position where the stop 50 is engaged. This movement of the belicrank lever will also f cause arm 39 to be swung in a counter-clockwise This gauge is provided with suitable indicia,

direction by means of link 44 since pin 45 is at the rear end of slot 46. The positions of the belicrank lever and arm 39 when moved by the cable are shown in broken lines. The position assumed by arm 39 is such as to place the shaft 32 in a position where the flat surface 33 is in a vertical position. When shaft 22 is rotated, lobe 34 moves cage 20 to the right, thereby unseating the valve element 26 and opening passage Il. Fluid under pressure will then enter the cylinder and move piston 29 to the left and compress spring 30 about half-way, provided the fluid pressure developed is slightly above four hundred and fifty pounds per square inch. As soon as the cage is moved to the right and fluid under pressure is admitted to the cylinder, the pressures acting on the opposite ends of the cage will become equal. The spring 28 can thus become operative to continue to move the cage to the right in order to cause seating of the valve element 24 and closing of passage ll. The master cylinder may now be released to its inoperative position and then subsequently, cable 44 released. Fluid under pressure will now be trapped in the system since the valve element 24 will be held in engagement with the seat by the action of the trapped fluid pressure. When cable 48 is released, spring 41 will be effective to return the belicrank lever to its normally inoperative position as shown in full lines in Figure 1. The arm 39, however, will not be returned due to the slot 46. The spring 41 cannot return arm 39 and cause unseating of the valve element 24 because the spring in its distended position does not exert enough force to overcome the action of the trapped fluid pressure holding the valve element 24 seated.

When fluid under pressure is caused to' be trapped, it is seen that this trapped fluid pressure is acted on by piston 24 and the compressed spring 30 and that ii there should be some contraction of the fluid which is trapped, the action of spring 30 and the piston will, nevertheless, maintain the trapped fluid under pressure. The trapped fluid will remain under pressure as long as the pressure does not fall below one hundred pounds per square inch. If it should drop to one hundrod pounds, spring 41 in its contracted position (bellcrank lever in released position) will be sumclent to move arm 39 back to its-normally inoperative position, thus causing the shaft to pull the valve element 24 off its seat against the action of the one hundred pounds of pressure which is tendin to hold it seated.

released. Also, the fluid under pressure which might be in cylinder IE will be forced out by unseating the valve element 26 and piston 29 will be returned to its inoperative position as shown in Figure 2.

It is to be noted that fluid pressure cannot-be trapped unless the master cylinder is releasedv fifty pounds per square inch, it will not be possible to trap fluid to hold the brakes applied. The reason for this is that as soon as cable 68 is released, the full force of the stretched spring #81 will be efiective to rotate arm 39 and ii the fluid under pressure is insufliclent (less than four hundred and fifty pounds per square inch) to hold- -the valve element zd seated against the force exerted by the spring tendingto unseat it, it will be unseated and, therefore, no fluid pressure trapped.

In order that the operator may be aware of the fact that there has been suiflcient fluid pressure developed to enable the fluid trapping device to become operable, the gauge 52 is provided. I This gauge may carry three indicating figures as shown, these flguresbeing 300, 450, and 600 to indicate these number of pounds per square inch. Thus if the operator thinks that he has suflicient pressure for the trapping device to operate, he will operate the trapping device by pulling on cable 48. This, as previously described, will connect the cylinder to chamber l and also place the gauge 52 in communication with the chamber. If the gauge now registers 450 pounds perfsquare inch or more, the operator will know that/the trapping devicecan be placed in operation and he 'will then release the master cylinder. If the gauge is below the 450 figure, heknows that the master cylinder must be further operated to increase the fluid pressure.

The gauge is also of value in informing the operator when the pressure of the trapped fluid -is becoming dangerously low and the trapping device may release the trapped fluid pressure. Ifthe arrow of the indicator should get below 300,

the operator is warned that additional fluid pres- I Ill account of this trapped fluid cause a quick drop in the pressure. Thus it is seen that the 300 figure should be considered as a danger flgure since at this time the spring-backed piston no longer is effective on the trapped fluid.

It is also to be noted from the arrangement of the actuating mechanism for the trapping device.

including the particular manner in which spring $1 is associated with the bellcrank lever and the shaft operating arm 39, that the operator in setting the trapping device need only employ a uniform pull notwithstanding the fact that spring 57 is being stretched. When cable 48 is initially pulled, the pull of spring 41 on the bellcrank lever is a minimum since said spring is in its minimum V stretched condition. Under these conditions the leverage ratio between the cable and spring is low. However, as the bellcrank lever is operated and the spring is stretched, the leverage ratio is increased and because of this, the input force need not be increased to continue to stretch the spring.- This uniform input effort is low and makes the operation easier for the operator.

From the foregoing it is seen that I have provided a trapping device for the fluid pressure system which cannot be made operative-unless the fluid pressure developed is'above a predetermined value.

sure of the trapped fluid will be available to continue to hold the brakes applied under nearly all conditions. The trapped fluid pressure can be very quickly released by merely operating the master cylinder. The operator is also always informed as to the condition of the trapped fluid by the reading of the gauge. If the gauge falls far below a certain point, he will be informed that there is a possibility-that the brakes are not being held applied as desired and the master cylinder should be additionally operated to bring this pressure up to a higher figure. Also a fall in pressuremay indicate a leak if there has been no great change in temperature.

, Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with a fluid pressure system having a source of pressure and a fluid pressure actuated device connected thereto, of manuallyactuatable means for trapping fluid under pressure in the actuated device to thereby permit release of the pressure at the source without release of the actuated device, said trapping means embodying means for preventing fluid under pressure from being held trapped notwithstanding manual actuation thereof unless the pressure developed'by the source and effective in the device is greater than a predetermined value.

2. In combination witha fluid pressure system having asouree of pressure and a fluid pressure actuated device connected thereto, of means for trapping fluid under pressure in the actuated device to thereby permit release of the pressure at the source without release of the actuated device, said trapping means embodying means for preventing fluid under pressure from being trapped unless the pressure developed by the source is greater than a predetermined value,-

and means for releasing said trapped fluid under This will insure that a high pres-- pressure by a reapplication of fluid pressure from said source.

3. In combination with a fluid pressure system having a source of pressure and a fluid pressure actuated device connected thereto, of means for trapping fluid under pressure in the actuated device to thereby permit release of the pressure at the source without release of the actuated device, said trapping means embodying means for prevening fluid under pressure from being trapped unless the pressure developed by the source is greater than a predetermined value, a chamber having a yieldable wall, and means for placing said chamber in communication with the trapped fluid only when said trapping means is operated.

4. In a fluid pressure system, a source of pressure, a device to be actuated, conduit means between the source and the device, a fluid cham her having a yieldable wall, means for simultaneousb placing said chamber in communication with the actuated device and for preventing return of fluid under pressure from said chamber and device, and manually-controlled means for causing the flrst named means to be operative and so remain. without the necessity of holding the manually-controlled means in a set position element seated is below a predetermined value.

8. In a fluid pressure system, a source of pressure, a device to be actuated by fluid pressure, conduit means between the source and the device and means .associated with the conduit means for trapping fluid under pressure in said device and permitting release of the pressure from the source without release of said device, said means comprising valve means having a valve element unseated in the direction of the flow of fluid from the source to the device and capable of being held seated by the trapped fluid under pressure, manually-controlled means for seating said valve element, spring-operated means for unseating the valve element when thetrapped fluid pressure acting to hold said valve element seated is but only if the fluid pressure developed by the source and effective in the device is above a predetermined value..

5. In a fluid pressure system, a source of pressure, a device to be actuated, conduit means between the source and the device, a fluid chamber having a yieldable wall, means of simultaneously placing said chamber in communication with the actuated device and for preventing return of fluid under pressure from said chamber and device only when the fluid pressure developed by the source and effective in the device is above a predetermined value, and means for releasing the fluid under pressure in the device and chamber by a rte-application of fluid under pressure from the source.

6. In a fluid pressure system, a source of presbelow a predetermined value, and means for varying the unsating force of said spring-operated means.

9. In a fluid pressure system, a source of pressure, a device to be actuated by fluid pressure. conduit means between the source and the device and means associated with the conduit means for trapping fluid under pressure in said device and permitting release of thepressure from the source without release of said device, said means comprising valve means having a valve element unseated in the direction. of the flow of fluid from the source to the device and capable of being held seated by the trapped fluid under pressure,

spring-controlled means forbiasing said valve element toward any unseated: position, spring means for seating said valve element, manual means for operating said spring-controlled means so as to permit said spring means to seat said valve element, said spring-controlled means being effective on said valve element to unseat the same whenthe trapped fluid pressure is below a predetermined value and said manual means is released, and means for varying the tension of the spring of said spring-controlled means by the manual means to thereby vary the force tending to unseat the valve element, said tension being greater when said manual means is in a position permitting seating of the valve element than when said manual means is released. I

10. In a fluid pressure system, a source of pressure, a device to be actuated by fluid pressure, conduit meansv between the source and the device and means associated with the conduit means for trapping fluid under pressure in said device ment, and spring-controlled means acting on said t valve element to unseat the same when seated but capable of unseating the element only when the trapped fluid acting to hold it closed is below a predetermined value.

- 7. In a fluid pressure system, a source of pressure, a device to be actuated by fluid pressure, conduit means between, the source and the device and means associated with the conduit and permitting release of the pressure from the source without release of said device, said means a spring for biasing said ,valve toward a seated capable of being held seated by the trapped fluid v position, a cam for unseating said valve and permitting it to be seated, a lever for operating said cam, a second spring acting on said lever to cause said cam to unseat the valve element, and manual means connected to said second spring and lever for simultaneously tensioning said second spring and for moving said cam so as to permit the valve element to be closed by its closing spring. the connecting means between said manual means and the second spring being such as to increase the tension thereon without substantial increase in manual effort on the manual means when the lever and cam are operated so that the valve'element can be closed and embody means permitting said second spring to have a decrease in tension when the manual means is released.

11. In a fluid pressure system, a source of pressure, a device to be actuated, conduit means bemovement, spring-controlled means for holding the first valve element closed and the second element open, and means for opening the first valve and closing the second valve element against the bias of the spring to thereby connect the chamber to the device and prevent fluid under pressure from returning to the source from the device, said valve element of the second named valve means being so arranged as to be held seated against the bias of the spring by-the fluid pressure in the device but only if said fluid pressure is above a predetermined value.

12. In a fluid pressure system, a source of pressure, a device to be actuated, conduit means between the source and the device, a fluid chamber having a yieldable wall, conduit means for placing said chamber in communication with the device, valve means for closing the last named conduit means, a second valve means for preventing fluid under pressure from returning tothe source from said device, means connecting the movable elements of the valves together for simultaneous movement, spring-controlled means for holding the first valve element closed and the second element open, and manual means for so moving the spring-controlled means against the bias of its spring as to open the first valve element and close the second valve element and thereby connect the chamber to the device and prevent fluid under pressure from returning to the source from the device, said valve element of the second named valve means being so arranged as to be automatically held seated by the fluidpressure in the device without manual eflort and against the un- 13. In a fluid pressure system, a source of pres sure, a device to be actuated by fluid pressure, a chamber having an inlet connected to the source and an outlet connected to the device, a second chamber having a yieldable wall and communicating with the first chamber by a portpositioned at a point opposite its inlet, connected valve elements positioned in said first chamber for alternately closing the inlet and the said opposed port which communicates with the second chamber, said valve elements being movable off their seats toward the interior of the first chamw ber, spring-controlled means for holding the valve elements in aposition where the inlet is open and the opposed port is closed. and manually-controlled means for increasing the tension of the spring and for simultaneously causing the valve elements to be so positioned that the inlet will be closed and the port open and the valve element for the inlet maintained closed if the fluid under pressure in the first chamber is above a predeter mined value. 4

14. In a fluid pressure system, a source of pressure, a device to be actuated by fluid pressure, a chamber having an inlet connected to the source and an outlet connected to the device, a second chamber having a yieldable wall and communicating with the first chamber by a port positioned at a point opposite its inlet, connected valve elements positioned in said first chamber for alternately closing the inlet and the said opposed port which communicates with the second chamber, said valve elements being movable ofi their seats toward the interior of the first chamber, spring-controlled means for holding the valve elements in a position where the inlet is open and the opposed port is closed, andmeans including manual means for controlling the movement of the valve elements so that the inlet will be closed and the port opened and maintained in such condition after release of the manual means by the action of the fluid pressure in the first chamber is sufficientlylgreat tohold tllinlet valve element seated against the unseating action of the spring-controlled means.

STEVE SCHNELL. 

